No abstract

Infectious bursal disease virus (IBDV) is the etiological agent of an immunosuppressive and highly contagious disease that affects young birds, thus causing important economic losses in the poultry industry. Multimeric particles with different architectures based on the capsid protein VP2 have been widely produced for different purposes. We hereby show the production and easy recovery of IBDV subviral particles (SVP) from transiently transformed Nicotiana benthamiana. The SVP, which were observed by electronic microscopy, proved to be antigenically and immunogenically similar to the virion. Indeed, anti-IBDV antibodies from samples of infected birds recognized these SVP and, when injected intramuscularly, these subviral particles also evoked a humoral immune response in chickens. We developed an in-house ELISA using SVP as coating reagent that demonstrated to be highly accurate and in good agreement with a commercial ELISA. This study demonstrates that the recombinant antigen generated and the technology used to produce it are suitable for developing a diagnostic tool against Infectious bursal disease.

The immune response elicited by the oral inoculation of an intermediate strain of infectious bursal disease virus was studied in chickens. A strong over expression of IL-6, IL-8, IFNα and IFNγ was observed in bursa at 3 days post inoculation together with an increase in splenic NO2 release. An influx of T-lymphocytes was also detected.

The complete nucleotide sequence of foot-and-mouth disease virus (FMDV) South American strain O(1) Campos/Bra/58 was determined. The 8,168 Kb sequence and the deduced amino acid sequence were compared to published FMDV sequences. They showed the highest sequence homology with the O(1) Kaufbeuren/FRG/66 strain, but closer evolutionary relatedness to the Argentinean strains.

Different immunogens such as subunit, DNA or live viral-vectored vaccines against Infectious Bursal Disease virus (IBDV) have been evaluated in the last years. However, the heterologous prime-boost approach using recombinant modified vaccinia Ankara virus (rMVA), which has shown promising results in both mammals and chickens, has not been tried against this pathogen yet. IBD is a highly contagious and immunosuppressive disease of poultry that affects mainly young chicks. It is caused by IBDV, a double-stranded RNA virus carrying its main antigenic epitopes on the capsid protein VP2. Our objective was to evaluate the immune response elicited by two heterologous prime-boost schemes combining an rMVA carrying the VP2 mature gene (rVP2) and a recombinant VP2 protein produced in Nicotiana benthamiana (pVP2), and to compare them with the performance of the homologous pVP2-pVP2 scheme usually used in our laboratory. The SPF chickens immunized with the three evaluated schemes elicited significantly higher anti-VP2 antibody titers (p<0.001) and seroneutralizing titers (p<0.05) and had less T-cell infiltration (p<0.001), histological damage (p<0.001) and IBDV particles (p<0.001) in their bursae of Fabricius when compared with control groups. No significant differences were found between both heterologous schemes and the homologous one. However, the rVP2-pVP2 scheme showed significantly higher anti-VP2 antibody titers than pVP2-rVP2 and a similar tendency was found in the seroneutralization assay. Conversely, pVP2-rVP2 had the best performance when evaluated through bursal parameters despite having a less potent humoral immune response. These findings suggest that the order in which rVP2 and pVP2 are combined can influence the immune response obtained. Besides, the lack of a strong humoral immune response did not lessen the ability to protect from IBDV challenge. Therefore, further research is needed to evaluate the mechanisms by which these immunogens are working in order to define the combination that performs better against IBDV.

Infectious Bursal Disease Virus (IBDV) causes a highly relevant poultry disease that affects young chickens causing, among other effects, immunosuppression. IBDV is a bi-segmented double stranded RNA virus. The smaller ORF of larger RNA segment encodes VP5, a 17-kDa non-structural protein. Although it is an important protein for viral replication cycle, the definition of its specific role and subcellular localization remains unclear. In the present work we demonstrate, using imaging techniques, that VP5 is not a type II transmembrane protein but an intracellular membrane-associated protein. This finding might provide evidences of VP5 interaction with cellular proteins and its functions.

Several reports have shown that baculoviruses (BVs) have strong adjuvant properties on the mammalian immune system. Recent studies of our group demonstrated the ability of BV to stimulate the innate immunity in chickens. In this investigation, we aimed to assess the potential antiviral effect of BV given both, before and after infectious bursal disease virus (IBDV). In the first case, specific pathogen free chickens were intravenously inoculated with 5 × 10(7) pfu of Autographa californica nuclear polyhedrosis virus and 3 h later were orally administered 2.5 × 10(5) egg infectious doses 50 of IBDV. In the second case, chickens received IBDV 3 h before BV inoculation. Five days later, chickens were bled and euthanized. RNA from the bursa was analyzed for cytokine production. Also, bursae were used for virus recovery, and processed for lymphocyte isolation. The results showed that the administration of BV 3 h after the inoculation with IBDV produced important changes in the effect that IBDV causes in the bursa. BV reduced the infiltration of T lymphocytes, decreased the expression pattern of IL-6 and IFN-γ and inhibited IBDV replication. The results herein presented demonstrate that this Lepidopteran virus shows antiviral activity in chickens under experimental conditions. Investigations under field conditions have to be done to probe this strategy as a valuable sanitary tool for the treatment and prevention of chicken diseases.

SUMMARYThe Bovine Viral Diarrhea (BVDV) virus causes numerous pathologies that range from reproductive losses to infections of little clinical significance in the bovine digestive tract. Variation have been reported among the strains of the BVDV, which are classified into two biotypes; cytopathogenic (CP) and non-cytopathogenic (NCP), and the viral types I and II. This work describes the pathological findings in a calf with diarrhea and severe thrombocytopenia. The strain isolated (334/3) was molecularly characterized by sequencing of the 5'non-coding region (5' NCR). These analyses revealed 90-98% homologies with reference strains type I strains and the changes associated with BVDV type II, were not found. INTRODUCCIONLa Diarrea Viral Bovina (DVB) es una enfermedad económicamente importante que afecta al ganado bovino y que afecta a numerosos países (Houe 1999). En Argentina, la enfermedad se encuentra ampliamente difundida en la región de la cuenca lechera santafesina, ubicada en la pampa húmeda, zona de intensa actividad agrícola-ganadera, como lo señalan trabajos previos realizados para la detección de anticuerpos en rodeos lecheros (Occhi y col 1991) y la prevalencia serológica descrita por otros autores (Muñoz y col 1996).La enfermedad se puede presentar en distintas formas, que van desde una subclínica a clínica hiperaguda o aguda hasta una crónica, acompañada por inmunodepresión que incrementa la susceptibilidad a patógenos secundarios. En su forma aguda, produce abortos, muertes perinatales, nacimientos prematuros y un amplio rango de malformaciones (Duffel y col 1986). En su forma crónica da lugar al nacimiento de animales persistentemente infectados (P.I.) e inmunotolerantes al virus (Bolin y Ridpath 1992), los cuales resultan de gran relevancia epidemiológica y son los responsables de la perpetuación del virus en la población bovina (Edwards y col 1987).Las cepas del VDVB presentan dos biotipos, no citopatogénicos (NCP) y citopatogénico (CP), diferenciables por el efecto que causan en cultivos celulares susceptibles in vitro (Clarke y col 1987). Dicha citopatogenicidad es una propiedad que depende tanto de los factores genéticos del virus como de los del cultivo celular utilizado. Se considera que el biotipo CP podría derivar del NCP por efectos de mutaciones y recombinaciones (Bolin y col 1992, Collet 1992). Estudios genéticos han demostrado que las mutaciones y rearreglos dentro de la región que codifica para la proteí-na no estructural p125 (p54/p80) están relacionados con la conversión del VDVB NCP a CP (Meyers y col 1992).Desde el año 1980 se han descrito aislamientos del VDVB capaces de causar una enfermedad aguda en el ganado inmunocompetente con un síndrome caracterizado por hemorragias equimóticas en las mucosas de varios órganos, siendo el rasgo distintivo de esas infecciones una severa trombocitopenia responsable de las lesiones observadas (Corapi y col 1989, Rebhun y col 1989). Los aislamientos identificados, capaces de inducir la enfermedad aguda, pertenecen a un linaje genético distint...